Wood-frame construction is a common and economical building technique for residential and commercial buildings. Spruce, Pine, or Fir (“SPF”) dimensional lumber, such as common 2×4's and 2×6's, are the primary structural members within wood-frame constructions. Most commonly, these structural members are placed in a standard arrangement, starting with a horizontal “bottom plate” that is typically fastened with bolts or nails to a planar floor surface, typically comprising concrete or wood. Onto this bottom plate are fastened multiple, parallel, vertical “studs”. These studs are typically placed at a predetermined spacing along the bottom plate of between 406 mm and 610 mm (16 inches and 24 inches) and are fastened at the top to one or more horizontal “headers”. This combination of interconnected horizontal and vertical structural members forms an immobile, rigid rectangular framing assembly known as a “stud-wall”. One or more wall coverings, such as siding, wall board, or laminated-wood sheets (e.g., plywood or Oriented Strand Board/OSB) are then affixed to the stud-wall to form vertical wall surfaces that may both define the building envelope and also divide the interior of the structure into individual rooms. A key feature of the stud-wall design in wood-frame constructions is that it incorporates a hollow wall cavity between the wall covering surfaces; the wall cavity is most commonly between about 100 mm to 150 mm in depth (4 to 6 inches), which provides sufficient internal space to contain other building elements such as electrical wiring, plumbing, climate control ductwork, and insulating materials, such as glass-fiber insulation batts.
In a flood event, wood-frame constructions may be adversely impacted by rising water. In particular, the structural members within wood-frame constructions, as well as the associated wall covering materials and any building elements within the wall cavities, may absorb excessive amounts of moisture. The exact quantity of water absorbed will of course depend on various factors, such as the portion of structural member surface-area that is exposed to moisture and the duration of the water contact. Within the Forest Products industry, the “Moisture Content” of wood is defined as the ratio of the mass of water within a given sample to the mass of the dry wood in that sample, and this measurement is reported as the percent moisture content (% MC). It is common for wooden structural members to reach 30% moisture content or greater even with only brief floodwater exposures.
Once wetted, it is essential that the structural members return to normal levels of moisture in order to prevent the growth of mold and fungus. Fungal growth is a significant threat to structural integrity of wood-frame constructions because fungi will actually consume wood, and if left unaddressed, will eventually compromise the building. Though mold does not directly impact structural integrity, mold growth is a known health hazard to building occupants.
In their publication, “Air Drying of Lumber”, FPL-GTR-117 (page 4), the U.S. Department of Agriculture teaches that Fungi cannot grow in wood with a moisture content of 20% or less. Additionally, the publication “A Brief Guide to Mold, Moisture, and Your Home”, EPA 402-K-02-003, from the U.S. Environmental Protection Agency, teaches maintaining wooden structural members at not more than 15% Moisture Content to avoid mold growth. Thus, it is understood that structural members must be returned to not more than 15% MC in order to eliminate the possibility of both mold and fungal growth within wood-frame constructions.
In the publication, “Initial Restoration for Flooded Buildings,” (FEMA 549, Appendix E, pp 9-12), the U.S. Federal Emergency Management Agency teaches the following steps to remediate stud-walls within a wood-frame construction after a flood event:                1. remove at least the lower portion of the wall coverings from the stud-wall surface,        2. extract any damaged building elements and/or wet insulation from within the wall cavity, and        3. allow the structural members within the stud-wall to dry.        
If these teachings are followed, one can typically expect excess moisture to evaporate from the structural members of flooded stud walls over a period of three-to-five weeks, although it may take longer if higher moisture content has been reached. It is of course apparent that the longer that wooden structural members remain above 15% moisture content, the greater the potential for biological growth to occur. Additionally, during the time that the walls are open and drying, refurbishment cannot proceed and the affected building is often unsuitable for use. It is therefore highly desirable to accelerate the process of drying these wet structural members. The electromagnetic wave (EMW) treatment method and apparatus of the present invention achieves such an improvement in drying speed.
U.S. Pat. No. 5,635,143 teaches a method and apparatus for the removal of contaminated concrete. It does not teach an EMW treatment method for the In-situ reduction of moisture content in a structural member within a wood-frame construction. The prior art apparatus comprises a microwave generator, a specially-inclined waveguide, and a vacuum system in order to demolish and extract material from the concrete surface to be cleaned. While there is some similarity to the inventive apparatus, it is clear that the requirement for an angled waveguide and vacuum system—elements not required in the drying apparatus of the present invention—is fundamental to the intended purpose of this prior art apparatus.
U.S. Pat. No. 3,721,013 teaches an improved Kiln-drying method for batches of green lumber, using a combination of radio-frequency energy, heated air circulation and humidity control. It does not teach an EMW treatment method for the In-situ reduction of moisture content in a structural member within a wood-frame construction. Instead, the subject Kiln method teaches the use of a large, stationary chamber into which are placed the pieces that are to be dried. Neither large-scale objects that exceed the dimensions of this chamber nor immobile objects can be treated in such an apparatus. Additionally, the prior-art treatment method is a lengthy process taking many days to complete and requiring the monitoring and adjustment of both temperature and humidity according to a specified “drying schedule”. By contrast, the portable EMW drying apparatus of the present invention is a small-scale device capable of easy movement from one geographic location to another. By intention, it is easily transported to the location of a previously flooded wood-frame structure and is capable of drying one or more of the constituent structural members in-situ. It will be immediately obvious that there are tremendous time and cost savings in not having to disassemble a wood-frame construction in order to dry its component structural members. Furthermore, the EMW treatment method of the present invention is far less complex in its implementation, given that there is no need to mimic the drying schedule of a lumber mill kiln.
Given the limited teachings in the art of post-flood remediation, it is clear that there is a need for a simple and expedient method of drying wood-frame structures. In particular, the general public would greatly benefit from an improved method for the In-situ reduction of moisture content in a structural member within a wood-frame construction. The Apparatus and Method of the present invention serve to address this unmet need.